Many motors with three degrees of freedom like ones using a piezoelectric element (refer to Published Unexamined Japanese Patent Application No. S62-228392, Published Unexamined Japanese Patent Application No. H09-34409, Published Unexamined Japanese Patent Application No. H09-219980, Published Unexamined Japanese Patent Application No. H11-18459 and PCT Publication Number WO 02/15358), ones using a synchronous motor (refer to Tomoaki Yano, Makoto Kaneko, “Basic Consideration of Actuators with Multi Degrees of Freedom Having an Identical Center of Rotation”, Journal of Robotics Society of Japan, Vol. 11, No. 6, pp. 875-882, 1993), ones using a stepping motor (refer to Tomoaki Yano, Takeo Suzuki, Masuo Sonoda, Makoto Kaneko, “An Actuator with Three Degrees of Freedom Having an Identical Center of Rotation (4th Report) Development of a Stepping Motor and its Basic Experiments”, Proceedings of Robotics and Mechatronics, No. E307, pp. 1210-1211, The Japan Society of Mechanical Engineers, 1994), and ones using an electromagnet (refer to Published Unexamined Japanese Patent Application No. S62-221856, Published Unexamined Japanese Patent Application No. H05-64417 and Published Unexamined Japanese Patent Application No. H09-168275) have been developed. In a case of detecting angles of three rotation axes by using three encoders, however, it is necessary for at least one encoder to be rotated together with a motor. Therefore, not only they must make their structure more complex, but also they must make torque of their motor more bigger than a desired amount. Moreover, they can decide a precise position in a case of using some stepping motors. However, even though they do not use the encoders, they have to rotate at least one stepping motor centering around at least one rotation axis. Therefore, as a position detection method for transfer organization with multi degrees of freedom, one using an acceleration detector (refer to Published Unexamined Japanese Patent Application No. H05-64417 and Published Unexamined Japanese Patent Application No. H09-168275), one using an electromagnet (refer to Tomoaki Yano, Makoto Kaneko, “An Actuator with Multi Degrees of Freedom Having an Identical Center of Rotation (6th Report) Position Control of the Multi-Pole Synchronous Motor”, 12th meeting of Robotic Society, No. 1354, pp. 193-194, 1994), and so on have also been developed. However, there are the following problems about these methods: For example, in a case of using an acceleration detector, their accuracy of a position becomes worse as time goes by because of accumulation of errors even though their structure is simple and can detect for all of three degrees of freedom without limit. In addition, in a case of using an electromagnet, weight of a device itself becomes heavy, a part detecting a line of magnetic force is desired, and the line of magnetic force has a bad influence on some electronic parts.
For applications of a motor with multi degrees of freedom, now, we can consider many cases that it has only to rotate freely within a specific range, for example, like a moving camera and a back mirror, besides a case of rotating endlessly around three rotation axes. Here, rotation with three degrees of freedom can be realized by using a spherical surface bearing if it is not necessary to drive like a motor (for example, refer to Published Unexamined Japanese Patent Application No. H07-317758, Published Unexamined Japanese Patent Application No. H09-166135 and Published Unexamined Japanese Patent Application No. 2000-304039). Therefore, it can detect rotation angles up to 180 degrees around two rotation axes, by installing an indication bar on a rotor of the spherical surface bearing, moreover by rotating two orthogonal guide rails by using the indication bar. This method, however, can not only detect an inclination angle of the rotor rotating centering around the indication bar, but also stop rotation of the rotor centering around the indication bar. Suppose then that a new guide rail is installed as it becomes parallel for either one of two guide rails. In this case, if a slider installed on the indication bar moves parallel along to the new guide rail, the guide rail can always keep inclination of the rotor constantly, without almost making an action range of two rotation axes narrow. In addition, for some applications like a moving camera and a back mirror, it is seldom necessary to rotate the rotor 360 degrees, centering around the indication bar. Therefore, if inclination of the rotor can be fine-tuned, a motor with multi degrees of freedom is practical enough. If the slider can slide along one of two guide rails which are parallel even though a gap between these guide rails varies, these guide rails can detect inclination of the rotor up to 180 degrees.
Considering these facts, since a guide rail and two guide rails which are parallel are combined so as to be orthogonal with each other, the number of rotation axes of these guide rails is two, where three encoders are desired to detect each rotation angle of the guide rails. In short, since it is not necessary for these encoders to move according to rotation of a rotor, the rotor comes to be able to detect rotation angles of three rotation axes easily. Of course, the rotor comes to be able to rotate independently around three rotation axes, by rotating these guide rails by actuators.
In the present invention described in claims, a rotation system with three degrees of freedom is developed, where one guide rail and two guide rails which are parallel are combined so as to be orthogonal, moreover some encoders installed on a base detect rotation angles of these guide rails. In addition, in the present invention described in claims, a rotation system with three degrees of freedom, which rotates these guide rails by using actuators installed on a base, is also developed.